Novel proton exchange membrane based on crosslinked poly(vinyl alcohol) (PVA) for direct methanol fuel cells (DMFCs)
Date Issued
2007
Date
2007
Author(s)
Liu, Chien-Pan
DOI
en-US
Abstract
Direct Methanol Fuel Cells (DMFCs) are promising new power sources for vehicles and protable devices. It’s significant challenge to develop proton exchange membranes (PEMs) possing both desired proton conductivity and low methanol permeability for the DMFCs. PEMs currently used in DMFC are perfluorinated polymers such as Nafion®. Even though such membranes have demonstrated good performances and long-term stability, their high cost and methanol crossover makes them unpractical for large-scale production. In this research, I describe two kinds of membranes and discuss respectively. The one is a novel physically and chemically PVA/HFA (PVA/hexafluoroglutaric acid) blending membranes with BASANa (Benzenesulfonic acid sodium salt) and GA (Glutaraldehyde) as binary reaction agents. GA and BASANa were used as cross-linkers and a donor of hydrophilic groups (-SO3H), which they both crosslinked to PVA chains for the acetalization reaction. Besides, HFA with dicarboxylic acid not only as the thermal cross-linking agent but also enhanced the flexibility and chemical stability. The other is to synthesize ampliplilic block copolymers on crosslinked acrylated urethane oligomer using UV-curing method. The amphiphilic block copolymers are synthesized using TEMPO controlled polymerization method with tertrabutylammonium styrenesulfonate (SSTBA) and divinyl benzene (DVB) as monomers for each block. This method has advantage synthesize the copolymer in one organic phase. Crosslinking of membranes of the copolymer are made by adding photo-initiators and subsequently being initiated by using UV light. By mixing acrylated urethane oligomer (AUO) with SSTBA monomer or PSSTBA-b-DVB copolymer and then add the crosslinker TAIC for third component. We can prepare PEM with excellent physicomechanical properties. These properties of the cross-linked PVA/HFA proton-conducting membranes or cross-linked acrylated urethane oligomer with sulfonated styrene membranes are examined by FT-IR/ATR spectroscopy, field emission scanning surface microscopy (FE-SEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), contact angle instrument, sorption studies, tensile test and AC impedance method. The feasibility of preparing films for DMFC application is investigated in this study. The proton conductivities and the methanol permeabilities of all two kinds of the membranes are in the range of 10-4 to 10-2 S/cm and 10-8 to 10-7 cm2/s, respectively, depending on its crosslinking density, and it shows great selectivity (Φ) compared with those of Nafion®-117. The possibility of using these PEMs for DMFC device is suggested.
Subjects
DMFC
質子交換膜
質子導電度
甲醇穿透度
交聯之聚乙烯醇
紫外光交聯
Acrylated urethane oligomer
Proton exchange membranes (PEMs)
Proton conductivity
Methanol permeability
Crosslinked PVA
UV-curing
Type
thesis
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